Enzyme kinetics 2 Flashcards
(25 cards)
What percentage of reactions are bisubstrate?
60%
Bisubstrate reactions are normally what type of reaction?
Transferase
Redox reaction
What are the two types of sequential reactions?
random - substrates enter in any order
ordered - substrates enter in a set order, B almost acts as an inhibitor to the reaction
What is a ping pong reaction?
One or more product released before all substrates have combined with the enzyme
What is the standard nomenclature for substrates?
A,B,C,D …. in the order they enter the enzyme
What is the standard nomenclature for products?
P,Q,R,S,T in the order they leave the enzyme
What is the general way in which lipases break down lipids?
Hydrolysing the ester of fatty acids
Where is triacylglycerol primarily secreted?
From the pancreas but also found in the salvia and stomach
What does phospholipase A2 cleave?
The second fatty acid from carbon 2 of a phospholipase
What metal is required in phospholipase A2 catalysis?
Ca2+
How does the triacylglycerol lipase work?
Learn the fucking mechanism bitch (dogs have seen lephricorns fucking)
What is the rate limiting step of phospholipase A2 catalysis?
The degradation of the tetrahedral intermediate
What is a monotopic protein?
Bound to one side of the membrane
What is a multispan protein?
A protein that spans both layers
Bacteria with one membrane are called
a) gram negative
b) gram positive
b) gram positive
gram negative 2 membranes
What is lipid A?
A lipid component of a lipopolysaccharide (LPS) which is responsible for toxicity of gram negative bacteria (part of outer membrane)
What catalyses the formation of Lipid A?
LpxC - it is a zinc dependant deacty/lase with two zonc ions bound in the active site. It catalyses
What does LpxC catalyse the deacetylation of?
UDP-3-O-GlcNac. This is the committed step of lipid A biosynthesis
Is histidine actively involved in the acetylation of UDP-3-O-GlcNac by LpxC?
Yes, this was the key difference in the alternative mechanism which is now believed to be true.
Glycotransferase (GT) and transpeptidase (TP) enzymes are involved in what?
The synthesis of the bacteria cell wall.
GT - catalyses the formation of the glycosidic linkage to form glycoside
TP - cross links the peptidoglycan chains to form rigid walls
What inhibits the activity of TP?
beta-lactams (e.g. penicillin), glycopeptides (e.g. vancomycin), and glycolipopeptides
(antibiotics)
GT transfers a WHAT from the corresponding sugar nucleotide donor substrate to a specific hydroxyl group sugar or to other acceptors (e.g. lipids)?
glycosyl residue
Peptidoglycan transglycosylation by the enzyme GT takes place through polymerisation of lipid II substrates. What is lipid II?
An amphipathic peptidoglycan precursor molecule involved in the synthesis of the cell wall of bacteria.
What does TP form cross links between?
Between the D-ala residues
